New Delhi: Mumbai and Kolkata are among the top 10 megacities across the world that face a serious threat due to rising sea levels owing to climate change, according to a report by Climate Central, a US-based research organisation. As many as 11 million people are at risk in Mumbai alone if the global temperature rises by 4°C, said the report released on Monday morning.

The report said that carbon emissions, causing 4°C of warming, could result into rise in sea levels that could submerge land, currently home to 470 to 760 million people. It could also mean unstoppable rise of sea levels over centuries to come. The report, however, added that aggressive carbon cuts, resulting in 2°C warming, could bring down the number of people who will get affected to 130 million.

According to the report, China faces maximum risk with 145 million people under threat due to rising sea levels, if emissions are not reduced.

Besides China, the report said 12 other nations, including India, Bangladesh, Indonesia and Vietnam, each have more than 10 million people at risk.

For instance, India has 55 million inhabitants endangered by 4°C warming, while 20 million at risk from 2°C warming.

Mumbai has 11 million people at risk after 4°C of warming; the number drops to 5.8 million in case of 2°C warming.

The report comes ahead of the meeting of ministers from more than 80 countries in Paris to find a common discussion ground before the global climate change negotiations at the Conference of Parties, under the UN Framework Convention on Climate Change (UNFCCC), in Paris starts on 30 November.

At the summit, countries will try and find a way to keep global temperature rise under 2°C by the year 2100. However, the United Nations recently said in a report that the world is not doing enough to control climate change.

The report builds on a paper authored by Climate Central scientists Benjamin Strauss and Scott Kulp, and Anders Levermann of Germany-based Potsdam Institute for Climate Impact Research published last month in the Proceedings of the National Academy of Sciences of the US.

“The outcome at Paris can point us toward losing countless great coastal cities and monuments around the world, unending migration, and destabilization, or toward preserving much more of our global heritage, and a more stable future,” said Strauss, PhD, vice-president for Climate Impacts at Climate Central and the lead author of the report.

Levermann, co-chair of the Research Domain Sustainable Solutions at the Potsdam Institute for Climate Impact Research in Germany, said, “Sea-level rise is nothing to be afraid of, because it is slow, but it is something to be worried about, because it is consuming our land, including the cities in which we create our future heritage today.”